How to Replace a Warped Subfloor in a Bathroom

by Laurie Reeves

Plywood or 3/4-inch 4-by-8 OSB sheets are used as materials for subfloors.

Once a subfloor warps underneath carpet, tile, hardwood or laminate flooring in the bathroom, it needs to be replaced as soon as possible. The subfloor may warp for any number of reasons, including an overflowing bathtub, shower or plumbing leak in the bathroom. Once water gets into the subfloor, the wood warps and fractures tile or cause carpets to develop mold and mildew. To prevent the spread of mold and mildew, remove and replace the warped subfloor with new wood as soon as possible.

1

Remove the existing baseboards and floor materials. Insert a pry bar, putty knife or flathead screwdriver between the wall and the baseboard at nailing locations. Gently pull the tool toward you to pull away the baseboard from the wall. Mark a number on the back of the baseboard with a felt-tip pen and transfer this same number to the wall, where it will be covered by the baseboard once reinstalled. This reduces the time spent trying to figure out which baseboard belongs where. Stack baseboards in another room out of the way.

2

Take off the carpet by lifting up one end with your hands and pulling it up from the carpet nailing strip. Wear gloves as you pull up the carpet. Insert a screwdriver underneath carpet nailing strips and lift up the strips that don't want to come up easily. Remove the carpet pad, if present. Discard the carpet nailing strips, the carpet and pad.

3

Dislodge tiles by inserting a pry bar or heavy-duty screwdriver underneath tiles and lifting up. Remove all tiles in the room and discard. To get at fasteners, use a putty knife to remove thinset and grout. To remove hardwood or laminate flooring, use a pry bar to get under the end of one of the flooring boards and lift up. Repeat this for all flooring boards to remove them and get access to the subfloor.

4

Vacuum the subfloor with a wet-dry vacuum to remove any dust or debris.

5

Examine the subfloor to see how it is secured to the floor joists. Properly secured subfloors are held in place by wood screws. If held by nails, use a claw hammer to remove nails. Insert the nail head between the claws of the hammer and tilt the hammer toward the nail head to lift and remove the nail. To gain momentum when removing nails, place a small block of wood under the hammer head as you lift the nail.

6

Unscrew the subfloor from the floor joists if held in place by screws. Use the appropriate screwdriver or drill equipped with a screwdriver bit to remove all the screws. If the screws are undamaged, you can use them again. Set them in a spare can for later use.

7

Start in a far corner of the room and lift up the subfloor. Standard uncut subfloor sheets are 4-by-8 feet, which may require you to get help in lifting up the plywood or oriented strand board. Insert the pry bar at the edge of a sheet of subfloor to lever the board away from the joists after removing all fasteners.

8

Replace the removed warped subfloor sheet with a new one. Note the locations of joists and secure the new subfloor to the joist using wood screws. Use screws two-and-a-half times as long as the depth of the subfloor. For instance if the subfloor is 3/4-inch thick, use a wood screw with a minimum length of 1 3/4 up to 2 inches. Secure the subfloor sheet to the floor joists every 6 inches.

9

Use the old subfloor section as a template to create the new subfloor section for specialty cut pieces around door entries. Lay the old board atop the new and mark around the edge of the old board with a carpenter's pencil. Cut out the new board following the pencil line using the circular saw.

10

Repeat Steps 7 through 9 until all subfloor sheets are removed and replaced.

11

Add a water seal agent to the new subfloor before adding cement or backer board for tile or a pad for carpeting. Let it dry before continuing.

Things You Will Need

Pry bar

Felt-tip pen

Claw hammer

Heavy-duty flathead screwdriver

Screwdriver or drill with screw bit

Wet-dry vacuum

4-by-8 sheets of plywood or OSB, 3/4-inch thick

Circular saw

Sawhorses

Nail or screw fasteners, 1 3/4 inch to 2 inches long, minimum

Water seal agent

Tips

Have safety goggles, gloves and a dust mask handy and use them while working, especially when cutting the new subfloor or removing the old.

Subfloor that shows no water damage or warping can stay in place. Only remove severely warped and damaged subfloor sheets.

Warnings

Use caution when working with power tools.

Cut subfloor sheets outside on sawhorses for best results. Avoid cutting sheets in the bathroom to prevent accidents.

About the Author

As a native Californian, artist, businessperson, contractor, journalist and published author, Laurie Reeves began writing professionally in 1975. She has written for newspapers, magazines, online publications and sites. In 2003, she and her husband moved into the home she designed, they built and decorated. Reeves graduated from San Diego's Coleman College.

Photo Credits

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